The present invention relates to an adsorber capable of selective removal of acidic contaminant gases in air atmosphere.
While air atmosphere is contaminated by various gases such as toxic gases and malodorous gases, acidic gaseous components are very versatile, including sulfur oxides, nitrogen oxides, chlorine compounds and sulfur-containing compounds such as hydrogen sulfide, as well as organic acid gases. A variety of methods have been proposed that are intended to purify air atmosphere containing these acidic gases. For example, it has been proposed that an acidic gas or mist be removed by reacting them with an alkaline substance. However, if the alkaline substance is used in a granular or particulate form, the reaction between the acidic gas or mist with the alkaline substance occurs on the solid's surface and the resulting salt precipitate on that surface will soon deprive the alkaline substance of its ability to remove acidic gases. If on the other hand, the alkaline substance is used in an aqueous liquid form, the aqueous solution will evaporate to cause a change in the concentration of the alkaline substance, thereby instabilizing the ability of the alkaline substance to remove acidic gases over time. With a view to solving these problems, removal of acidic gases by an ion-exchange resin has been proposed.
This method, however, is not an ideal solution. If an anion-exchange resin is used to remove an acidic gas or mist, carbon dioxide in the air is also removed and the amount of acidic gas that can be removed is smaller than when no such adsorption of carbon dioxide occurs. The effects of carbon dioxide are not significant if the gases to be removed are strong acids such as nitrogen oxides and sulfur oxides, but in the case of weakly acidic gases such as hydrogen sulfide, the effects of carbon dioxide are so pronounced as to cause a loss in the ability of the ion-exchange resin to remove acidic gases. This probelem with carbon dioxide is not limited to ion-exchange resins but is unavoidable if one wants to remove contaminant gases from air atmosphere through the reaction of neutralization between acid and base. Carbon dioxide would cause adverse effects on the human body if it were present in high concentrations but if its concentration is as low as it is in ordinary air atmosphere, it is harmless and need not be removed. Therefore, a need has existed for the development of a method or material that is capable of selective removal of non-CO.sub.2 acidic gaseous components without being adversely affected by carbon dioxide.